How Stress And Sleep Loss Are Shortening Your Life

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Late nights make for more sick days

Would you prioritize sleep if you knew it kept your immune system strong? That's the question the American Academy of Sleep Medicine wants you to ponder this week. Lost in the hoopla surrounding Independence day was the publication of some eye-opening (or eye-shutting) research by the American Academy of Sleep Medicine showing that the immune system responds sharply to sleep loss.

In the study, intimidatingly named “Diurnal Rhythms in Blood Cell Populations and the Effect of Acute Sleep Deprivation in Healthy Young Men,” Researchers at the Erasmus MC University Medical Center in Rotterdam, the Netherlands, and the University of Surrey in the UK measured white blood cell counts in young men who sleep eight hours and men whose sleep was restricted, and found a spike in white blood cells, particularly those called granulocytes, released in response to immune system threat.

The researchers' conclusion: Severe sleep loss jolts the immune system just as stress does (read on for more on stress).

In addition to shocking your immune system, lack of sleep also raises your stroke risk - even if you're relatively young and healthy. New research, presented last month at SLEEP 2012, found that those who cut back their sleep to less than six hours of sleep a night are at 4.5 percent greater risk of having a stroke compared with those who slept 7 to 8 hours a night. Though researchers don't know the exact mechanism, it seems that chronic lack of sleep causes inflammation, elevates blood pressure and heart rate, and affects glucose levels, leading to a much higher stroke risk in the sleep-deprived.

Most concerning, though, is that the 5,000+ people studied were healthy, middle-aged adults with a body mass index in the normal range -- not those typically considered at high stroke risk. And their sleep loss wasn't as extreme as in the immune study; these folks reported getting less than six hours of sleep a night - the amount that 30 percent of the American population reports getting.

This isn't news; study after study has shown that stress raises our risk of cancer, heart disease, allergies, and susceptibility to colds and flu. What's new is that researchers at Carnegie Mellon think they now know how this works. The key, they say, is cortisol, the stress hormone released whenever we feel fear, worry, or anxiety. Cortisol is supposed to give us a jolt of energy, enabling us to react to and run away from the lion as it were. But it appears that when our systems are constantly bathed in cortisol, the body loses its ability to regulate inflammation.

Here's how it works. Cortisol has a secondary function of controlling the body's inflammatory response to immune system triggers. But over time, with constant exposure to stress and therefore cortisol, tissues become less sensitive to cortisol, releasing less of their anti-inflammatory substances. (A similar process occurs with diabetes, as chronically elevated insulin leads to insulin resistance.)

The Carnegie Mellon team, headed by Sheldon Cohen, ran two tests of this theory. First they exposed healthy adults to cold viruses, isolating and monitoring for five days afterwards. People who'd recently been under stress showed increased resistance to cortisol. In a second test, the researchers found that participants had higher numbers of cytokines, which trigger inflammation.

So what does it all mean? That when you get stressed out and stop sleeping, or stop sleeping well, you get sick. (Think back to college, when you'd get a horrible flu or even pneumonia or mono, right after finals were over.) That probably doesn't seem that concerning; we've dealt with the post-all-nighter flu all our lives. But this year has also seen convincing research that the body's immune response is key to protecting us from serious disease, such as cancer, and that inflammation is a key precursor to heart attack, stroke, diabetes, and other life-threatening diseases. In fact, ongoing research is underway to document the effects of stress and sleep loss on shortening lifespan.

So take your stress reduction strategies seriously and get to sleep, darn it!